Small-punch die construction



March 13, 1956 M D. HEYMAN SMALL-PUNCH DIE CONSTRUCTION Filed May 22,1952 MN 1 J J a M I. V

IN V EN TOR.

United States Patentfi 2,738,008 SMALIi-PUNCHDIE CDNSTRUCTIONF Moses-D.Heyman, .Wd1nere, N I Y. ApplieationMay'n, 1952, SerialNo. 289,350 2Claims. (Ci. 164- 86) Thisinvention relates to punch and dieconstruction and, while the same-- is applicableto die setsgenerally,=-it' is more particularly adapted for application to die setsin" which'the punch elerr'rent's are' so smalland, therefore; fragile;that their'breakag'e'; for one'reason or another, is

quite frequent.

I'n punched out relatively small non-metallic 'parts' having one or moreperforations therein, the perforations are producedby punchelementsset-as insertsinto the die punch, said elements cooperating witlfa die;inane conventional manner, to pierce through a sheet or? strip ofmaterial. The perforations may have variou's sh-ap'es and may be small,frequently'dn"the- 'nature of f'iri di ameter or width. For in'stari'ce,inthe' produetion o mica bridgepie'ces'such as use'd iri electronic:tubes, the punch' manyas a dozen or nieresmall punch elements; all within a half inch or snialler circle and 'someof theseel'elrients obviateloss attending production of faulty 'pa-rt'sf- When such breakage of a'puneli is not immediately discovered,

manythous'ands of arts may'be produced With oiie"or more perforationsmissing tli'erefrornand'the sa'rne'rnust Since-die set'spi'oducingj"such stri'a'll parts are' re1ativ'e1y* small and, it' bein'gdifficiiltaird tirrie-consumin'g to ir'isp'eet the punch elements beforeeach operation- 0f the press that mounts the'die set, visual detectionis eeonorr'iie'allyunfeasible. Another object of the invention,therefore;'is-

to" provide means automatically" stopping 0i stalling-' the press shouldone or more of a the punch elements"* be broken or should oneormore" oftherrr be" improperly seated inithe'ipunch; Thus; uponisuc'h'abnormal"condi tion, the present meanswill iminediately stop"operationof the press and l the operation :can be restored only when theabnormalfcondition is correctedsi Another object of the invention is toprovide :anelectric circuitthat controls'the operationof the pressan'd-to include all :ofthe punch elements in:series in saidcircuit sothat abnormall removal of any onesuchelement from a the circuitWill-open thesamein the manner of a switch and stop the operation ofthe-press;

Theforegoing and other objects, features and-advantages of the inventionWi1l'become*more'clear1y evidentas-the following deseriptionprogresses,--said description havingbasis onthe-preferred but exemplaryform ofthe invention illustrated in the accompanying drawing.

In the drawing:

Fig; 1 is aside elevatiorial view ofa punch'press show-' ing a die setmounted thereon and provided with the presentnovel-means'connectedtosaid'die set for corn trollin'g'the"operationofthe*press:

inimed-iatelyde ecting 2,738,008 Pfi'tented Mar. 13, 1956' r Fig," Zis"a: greatlyf enlarged vertical sectional"view of thedie set'shown in Fig.1.

Fig. 3 isap'lan View of the "die of said die set. 'In" the drawing; Fig;1 shows a generally conventional one=revolution "punchpre'ss thatcomprises a frame 5' having a bed 6 and mounting a ram 7movabletoward'and' from" saidbed by crank'or' similar mechanism 81 Saidmechanism is driven fron'r'a shaft9 by a motor 10 conn'ect'e'd todrivea'ny'wneern on said shaft. While not shown; a conventional.one-revolution clutch operatively connects"shaft"9 and flywheel 11. Adie set'12, com

prisin'g'a are-1s mounted onbed6' and a punch 14 carried byrarn 7, isshown intypicalposition' in the press to adapted to be firmly"secur"edtopress" bed 6 and, according to the disposition, number andsizeoftlieperforations in apiece 21' to be punched 'o'u'tof strip'l;said die is providedwith'shea'rperforations '17 a'tits first stage andwith a she'arpe'rforatiorr'18at its second stage. The punchingsfrom'tliapie'ces 21- are? fanned in and' fall downwardly throughshear.perforations 17, and the punched out 'pi'eces 21"fa'll through'shearperforation 18into a collecting chute cliut'e'or tube 19. Should tube" 19 became filled with pieces 21" beforethe' saniec'a'n beernptied, the"magnetic bott'o'mZUWil'l be foreed away fromtube'19'by' the ressure onthe stack of pieces in said tube, as created by. the unch th'a'tsli'e'ars" out said pieces. Normally, however; whena'suitabl'e quantityof picc'es'liasbeen produced," the. sameare removedafte'rmanualdisplacement of bottom 20.

V The punch 14 comprises a metal block 22 which, in its mounts a' set ofmetal punch elements 213': aligned with and adapted to enter shearperforationslT first stage,

afterdraying first'shearedthrough work strip 15. These punch elements,of course; conformin size and shape to therespectiveperforations 17;Said elements 23rare providedas'insferts th'at' arereadilyreplaced ifdamagedor broken; Thus, each element 23is' formed to have 'a'shan'if24tigh'tlyyetremovably'engaged in block 22. Atit's second stage, block22 carries a punch elementES that sitnila'rly'coac'tswith shearperforationlSto punch pieces A conventional stripper plate 25 is carriedby punch block 22 and is resiliently p'ressed'by springmeans 27'tohold-work strip 15"down"against'dieblock 16 duringth'e timeth'at thepunch elements are being projected and'retracted i nto and'outof theirrespective perforations. A stud or tongue 28 on the punch block 22, inthe usualmanner,- constitutes the means effecting connection of punch14- to ram 7.

The-foregoing is generally conventional for progressive die sets thatpunch out perforated pieces from a work strip. It will be understoodthat the stage embodying, perforation 1'8"and punch element 25 may beomittedif' only a" perforated-work strip is to be produced or saidAccording to the present-invention, means-is provided for stopping theoperation of the press upon an abnormal condition in the die set 12, aswhen one or more of the punch elements 23 are broken or improperlyinserted in the punch 14. In this disclosure, the press is stopped byopening the electric circuit to motor 10. The press may be stopped inother ways as by locking the one-revolution clutch open so that there isno drive to shaft 9, or by simultaneously setting a brake on the crank 8or flywheel 11 when the motor circuit is opened.

The present novel means comprises three interconnected electric circuitsfrom a line or current source 29, 30. One circuit 31 controls motor thesecond circuit 32 is closed when ram 7 is retracted and open when saidram is projected and controls circuit 31; and the third circuit 33 isopen when the ram is retracted and closed when the ram is projected andalso controls motor circuit 31. Either circuit 32 or 33, when closed,will close the motor circuit. If both circuits 32 and 33 are open at thesame time, the motor circuit will also be open and the press cannotoperate.

Circuit 31 is shown as comprising a bridging plate 34 for a pair ofterminals 35 and 36, a connection 37 from terminal 35 to one pole ofmotor 10, a connection 38 from terminal 36 to line conductor 29, and aconnection 39 between the other pole of the motor and line conductor 30.It will be clear that when plate 34 is in bridging contact withterminals 35 and 36, motor 10 is in circuit with the current source.

Circuit 32 includes a solenoid 40 on the floating 41 core on which iscarried bridging plate 34, and also includes a switch 42 that is mountedon press frame 5 in operative association with an adjustable actuatorscrew 43 carried by ram 7. Said solenoid and switch are arranged in aseries circuit with line 29, 30, of which circuit a connection 44extends between line conductor 29 and switch 42, a connection 45 extendsbetween said switch and said solenoid, and a connection 46 extendsbetween said solenoid and line conductor 30. From the foregoing, it willbe seen that when ram 7 is retracted, solenoid 40 is energized bycircuit 32, because switch 42 is normally closed, to cause projection ofplate 34 into bridging contact with terminals 35 and 36 to, thereby,close motor circuit 31, and that when the ram moves toward its projectedposition, near the end of such movement, actuator 43 engages button 47of switch 42 to open the latter and circuit 32. Since said solenoid isnow deenergized, gravity or suitable spring means retracts core 41 andmoves plate 34 to open the motor circuit 31.

Circuit 33 includes the mentioned solenoid and circuitclosing means 48provided in die set 12.

The means 48 includes the mentioned punch elements 23 and a set ofmetallic die elements 49 carried by block 16, two terminals 50 and 51connected to the latter elements, and metal pieces 52 that electricallyconnect the upper ends of shanks 24 of the punch elements in pairs. Saidpunch elements 23 and pieces 52 are electrically insulated from block 22by being set in a solid and strong insulating block 53 of phenolic resinor phenolic resinimpregnated cloth or paper. In any case, the punchelements are arranged as electrically connected pairs which can only beconnected in series circuit when entered into and engaging die elements49. Stripper plate 26, if one is used in the die set, is preferably madeof an insulating material similar to block 53, or at least so made asnot to short the pairs of punch elements. The set of die elements 49, ina similar manner, is insulated from die block 16 by an insulating block54 in which said die elements are set. Said set of die elements 49comprises singleperforation blocks 55 and 56 and one or moreintermediate two-perforation blocks 57. The number of the latter blocksdepends on the number of pairs of punch elements provided in the punch14. The shear perforations 17 are provided in said set of die blocks.Terminal 50 is connected to block 55 and terminal 51 to block 56. Bythis arrangement, when the punch elements are entered in perforations17, a series electric circuit is closed between terminals 50 and 51.

The arrangement may be reversed with the die blocks arranged in pairsand the end punches of a set of punch elements provided with terminals50 and 51.

It will be seen from the foregoing that punch elements 23, aftershearing through work strip 15, enter perforations 17 and makeelectrical contact with the die blocks 49 and that a series circuit,starting with terminal 50 and following the path shown by the dottedarrows to terminal 51. It will be clear that the means 48 constitutes aswitch in circuit 33 since said circuit is open when the punch elementsare elevated or retracted from the die elements. It will also be seenthat the circuit shown by said dotted arrows becomes interrupted shouldone or more of the punch elements be broken or should one or more ofsaid elements be improperly seated and out of contact with one or moreof the pieces 52. Thus, upon such an abnormal condition in the die set,circuit 33 will not close. Should there be an odd number of punchelements 23 in the punch, a dummy element may be provided and placedoutside the periphery of the piece to be punched out and even outsidethe path of strip 15.

A connector 58 connects terminal 50 with connector 45 and solenoid 40,and a connector 59 connects line conductor 29 and terminal 51. In thismanner, switch 42 and the die circuit 48 are connected in parallel, saidswitch holding the motor circuit 31 until die circuit 48 is closed, atwhich time actuator 43 opens said switch and the motor circuit is heldclosed by said die circuit.

If conditions are normal, the press will operate to suecessively producepieces 21 since each projection of the ram causes open circuit 33 toclose as closed circuit 32 opens, and each retractive movement of saidram causes closed circuit 33 to open and open circuit 32 to close. Themotor circuit 31, therefore, remains closed at all times. However, underone or the other abnormal conditions mentioned, circuit 33 will remainopen after circuit 32 is opened by actuator 43. Since there is nocurrent in solenoid 40, the same becomes de-energized and plate 34leaves contact with terminals 35 and 36 to open motor circuit 31.Therefore, the motor will stop.

It will be realized that the work strip 15 must be of non-conductingmaterial otherwise the die circuit will not be operative as abovedescribed.

While I have described what I now regard as the preferred form of myinvention and being aware that modifications thereof may be made, Idesire to reserve to myself such modifications and variations of myinvention that may fall within the spirit and scope of the appendedclaims.

Having thus described my invention, what I claim and desire to obtain byLetters Patent, is:

1. The combination with a press having a bed and a ram and provided withmeans to reciprocate the ram relative to the bed and with a driver forsaid means: of a die unit affixed to the bed and provided with metallicblocks having shear perforations, said blocks being insulated from eachother and from the die unit; a punch unit carried by the ram andprovided with metallic punch elements arranged to enter said shearperforations after piercing through a non-metallic work piece interposedbetween the die and punch units, said punch elements being insulatedfrom the punch unit; means electrically connecting said punch elementsin pairs; said punch elements, when entered in the mentioned die blocks,and said element-connecting means combining to form a series electricswitch circuit; a current source for said switch circuit; a parallelelectric circuit across the switch circuit and including anormally-closed switch; means carried by the ram to open said switchafter said punch elements enter said perforations; an electric circuitfor the driver of the ram; and a control for the driver circuit by saidparallel circuits comprising electrical connections between saidparallel circuits and the driver circuit including a solenoid-controlledswitch in the latter circuit. v

2. The combination according to claim 1: a solenoid in series with saidparallel electric circuits and energized only when one or the other ofsaid parallel circuits is closed; said solenoid-controlled switch beingarranged to be closed only when the solenoid is energized.

References Cited in the file of this patent UNITED STATES PATENTSTiffany Oct. 23, 1945 Ekstrom et al Nov. 2, 1948 FOREIGN PATENTS AustriaJuly 10, 1916 Germany Feb. 12, 1920

